[PATCH 2/5] dt-bindings: watchdog: gpio: Describe minimum heartbeat intervals

[Florian Fainelli <f.fainelli@gmail.com>]

Some GPIO-controlled watchdogs require a minimum interval between input
transitions. Add an optional hw-min-interval-ms property to describe this
constraint, allowing the watchdog core to defer early keepalives.

Also remove the 16-bit limit on hw_margin_ms. The generic GPIO driver has
no hardware register imposing this limit, and its heartbeat interval is
stored in an unsigned int. The MTX-1 watchdog has a nominal 100-second
hardware timeout and requires at least 1.6 seconds between transitions.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 .../devicetree/bindings/watchdog/linux,wdt-gpio.yaml  | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/watchdog/linux,wdt-gpio.yaml b/Documentation/devicetree/bindings/watchdog/linux,wdt-gpio.yaml
index 499f1b7e03f9..1adbfe5e5461 100644
--- a/Documentation/devicetree/bindings/watchdog/linux,wdt-gpio.yaml
+++ b/Documentation/devicetree/bindings/watchdog/linux,wdt-gpio.yaml
@@ -36,7 +36,12 @@ properties:
     description: Maximum time to reset watchdog circuit (milliseconds).
     $ref: /schemas/types.yaml#/definitions/uint32
     minimum: 2
-    maximum: 65535
+
+  hw-min-interval-ms:
+    description:
+      Minimum time between watchdog resets in milliseconds. If omitted, the
+      watchdog can be reset at any time. Must be less than hw_margin_ms.
+    minimum: 1
 
   always-running:
     type: boolean
@@ -64,5 +69,7 @@ examples:
         compatible = "linux,wdt-gpio";
         gpios = <&gpio3 9 GPIO_ACTIVE_LOW>;
         hw_algo = "toggle";
-        hw_margin_ms = <1600>;
+        hw_margin_ms = <100000>;
+        hw-min-interval-ms = <1600>;
+        always-running;
     };
-- 
2.53.0